The Dynamics of Multiple Populations in the Globular Cluster NGC 6362

TL;DR

This study uses N-body simulations to show that the Milky Way's tidal forces can accelerate the mixing of multiple stellar populations in globular clusters, explaining the observed uniform distribution in NGC 6362.

Contribution

It demonstrates that tidal stripping can significantly hasten the spatial mixing of multiple populations in globular clusters, aligning models with observations of NGC 6362.

Findings

NGC 6362's populations are fully mixed due to high mass loss.

Clusters lose 70-80% of initial mass before complete mixing occurs.

Tidal effects accelerate the natural relaxation-driven mixing process.

Abstract

We investigate how the Milky Way tidal field can affect the spatial mixing of multiple stellar populations in the globular cluster NGC 6362. We use $N$-body simulations of multiple population clusters on the orbit of this cluster around the Milky Way. Models of the formation of multiple populations in globular clusters predict that the second population should initially be more centrally concentrated than the first. However, NGC 6362 is comprised of two chemically distinct stellar populations having the same radial distribution. We show that the high mass loss rate experienced on this cluster's orbit significantly accelerates the spatial mixing of the two populations expected from two body relaxation. We also find that for a range of initial second population concentrations, cluster masses, tidal filling factors and fraction of first population stars, a cluster with two populations should be mixed when it has lost 70-80 per cent of its initial mass. These results fully account for the complete spatial mixing of NGC 6362, since, based on its shallow present day mass function, independent studies estimate that the cluster has lost 85 per cent of its initial mass.